Vents for centrifugal casting molds



Oct. 18, 1960 J. M. CRANFORD EI'AL 2,956,322

VENTS FOR CENTRIFUGAL CASTING MOLDS Filed March 31, 1959 INVENTORS 8 JOHN M ORA/VFORD 30 1 ROBERT L. TEAGUE 32 WILL/AM H. WRIGHT BY gm, /%7/k ,v 5m

ATTORNEYS United States Patent VEN IS FOR CENTRIFUGAL CASTING MOLDS John M. Cranford, Robert L. Teague, and William H. Wright, Birmingham, Ala., assignors to American Cast Iron Pipe Company, Birmingham, Ala., a corporation of Georgia Filed Mar. 31, 1959, Ser. No. 803,254

17 Claims. (Cl. 22-1135) This invention relates to molds for use in the centrifugal casting of tubular metal articles, such as cast iron and steel pipes and tubing, and is particularly directed to a novel form of vent for such molds, especially molds which are lined centrifugally with refractory compositions containing relatively fine sand and combustible materials such as resin binders.

Whenever the composition of the lining of a centrifugal casting mold is such that gas is produced therein by the heat of the molten metal during the casting operation, it is necessary that the mold be provided with vents of sufiicient number and size to permit the ready escape therethrough of substantially all of the gas so generated. It is also necessary that these vents be so constructed that, when the lining is formed centrifugally, the lining material is not thrown out through the vents under centrifugal force so as to leave voids or weak spots in the lining at the inner ends of the vent holes which might permit the casting metal to enter the vents and stop them up, as well as make it more diflicult to strip the casting from the mold.

As one example of the type of mold wherein the present invention finds particular utility, reference may be had to US. Patent No. 2,731,690, dated January 24, 1956, which discloses a mold having a centrifugally formed, resin bonded sand lining and vents which are so designed and dimensioned as to become partially filled with the resin-sand mixture during the lining operation, without permitting any substantial loss thereof outwardly through the vents, the filling being sufficiently permeable to enable ready escape therethrough of the gases formed during casting. The form of vent shown in Patent No. 2,731,690 functions quite satisfactorily for approximately 50 to 60 castings, but it then becomes necessary to clean the vents by removing the gummy residue which is deposited therein as a result of burning of the resin component of the lining during the casting operation. With the form of vent shown in said patent, the cleaning operation requires removal and replacement of the packing and the perforated metal packing retainer in the outer end of each vent, and thus involves the expenditure of considerable time and labor.

The principal object of the present invention is to provide a new and improved vent construction for centrifugal casting molds of the character described which effectively performs the essential function of permitting the free passage of gas during the casting operation without the escape of lining material during the lining operation, and which is quickly and easily cleaned whenever necessary.

Another object is the provision of a novel form of mold vent which requires cleaning less frequently than the types of Vents previously used, and which also prevents the entrance of molten metal into the vent hole during the casting operation.

These and other objects will appear more fully upon consideration of the detailed description of the embodi- "ice ments of the invention which follows. In this connection, it is to be expressly understood that the specific structures hereinafter described and shown in the accompanying drawing are illustrative only, and are not be construed as representing the full scope of the invention defined in the appended claims. It will also be recognized that, while the vent construction of the present invention is particularly well adapted for use in molds which are provided with resin bonded sand linings as described in the above-mentioned Patent No. 2,731,690, it is also useful in molds having other types of linings, such as that formed by a flowable slurry in the manner disclosed in the copending application of Edwin H. Phelps, Serial No. 764,779, filed October 2, 1958.

In the drawing, wherein like reference characters indicate like parts throughout the several views:

Fig. l is a fragmentary side view, partially in section, of the bell end of one form of refractory lined pipe casting mold embodying the improved vent construction of the present invention;

Fig. 2 is a sectional View on an enlarged scale of one of the vents of the mold shown in Fig. 1, the section being taken substantially on line 2-2 in Fig. 3;

Fig. 3 is a top plan view of the vent of Fig. 2;

Fig. 4 is a transverse sectional view taken substantially on line 4-4 in Fig. 2; and

Figs. 5, 6 and 7 are end views, and Fig. 8 is a fragmentary side view, of modified forms of the core member of the vent shown in Fig. 2.

In Fig. 1, the vent construction of the present invention is shown, for purposes of illustration, as it would be incorporated in a metal mold 11 which is adapted to be used in the centrifugally casting of hell and spigot pipe, and is provided with a refractory lining 12 of any suitable character, such as the resin bonded sand lining described in Patent No. 2,731,690. In order to enable free escape of the gas which is formed in lining 12 during the casting operation, the mold is provided with a plurality of vents, I

indicated generally at 13, which are distributed more or less uniformly over the entire length of the mold. The number and positioning of the vents should be such as to permit ready escape therethrough of substantially all of the gas generated in lining 12 as a result of the heating effect of the molten metal, and will depend upon a number of factors, such as the thickness of the lining, the amount of resin binder or other combustible substances therein, the grain size of the lining sand, the character and thickness of the facing, if any, on the lining, and the temperature of the metal being cast.

As shown best in the enlarged view of Fig. 2, each vent 13 comprises a drilled hole extending through the body or wall of mold 11 in a substantially radial direction and having outer and inner portions 14 and 15 of different diameters. Outer portion 14 extends inwardly from the outer surface of the mold for a distance somewhat less than its diameter, while inner portion 15, the diameter of which is substantially smaller than that of outer portion 14, is relatively elongated and opens into the interior of the mold. The adjacent ends of the inner and outer portions of the vent hole are connected by a shoulder 16 which is preferably inclined at a suitable angle relative to the axis of the hole, instead of being perpendicular thereto.

Coaxially disposed within the vent hole is an elongated core member 17 of non-circular cross section, having a length equal to or slightly less than the thickness of the mold wall 11, which cooperates with the surrounding wall of inner portion 15 of the vent hole to form a plurality of restricted passageways 18 for the escape of gas from the interior of the mold, and which also serves to scour the vent hole in the manner hereinafter described whenever it becomes necessary to clean the vent. In the preferred embodiment illustrated in Figs. 24, core member 17 is hexagonal in cross section and has a circumscribed circle diameter such as to enable it to fit snugly within inner portion 15 'of the vent hole, but with sulficient clearance between its longitudinal edges andthe wall of the vent hole to enable rotation therewith;

Although the dimensions of the vent hole and core member may vary in molds of different sizes and with different mold lining compositions, it has been found that the purposes of the present invention are well fulfilled in the casev of molds having centrifugally formed, resin bonded sand linings of the character described in Patent No. 2,731,690 by the use of a vent hole wherein the di ameter and length of the outer portion 1 are approxiinately inch and Z/ inch, respectively, the inner por tion 15 has a diameter of inch, half that of outer portion 14, and the shoulder 16 makes an angle of approximately 60 with respect to the axis of the vent hole, in combination with a hexagonal core member 17 having a uniform inscribed circle diameter of /8 inch; This combination provides six restricted venting passageways 18 between core member 17 and the wall of inner portion 15 of the vent hole each having a cross-sectional area of appr 'ximately .004 square inch, or a total venting area of about .025 square inch, substantially equal to that which would be provided by an unrestricted circular hole having a diameter slightly less than inch.

Each vent 13 also includes means for rotatably supporting core member 17 in the vent hole with its inner end substantially flush with the inner surface of the mold wall, and for retainin the core member in this position against axial displacement either outwardly under the influence of centrifugal force or inwardly by an externally applied force. 7

In the embodiment illustrated, the core member supporting means comprises a plurality of threadless nuts or fasteners 19, 2i and 21 of the well known push-on type housed in the enlarged outer portion 14 of the vent hole, each of which fasteners consists of an annular body of resilient sheet metal cut or slit along radial lines to form a plurality of inwardly extending flexible teeth 22, The innermost fastener 19 is so disposed that its periphery seats against the shoulder 16 of the vent hole and its teeth 22 are flexed or bent inwardly, toward the interior of the mold, in frictional gripping engagement with the periphery of core member 17 so as to resist outward movement of the latter. Fasteners 29 and 21 are stacked on top of fastener 19 and have their teeth flexed in the opposite direction, i.e., outwardly toward the outer surface of the mold, so as to resist inward movement of core member 17. In order to lock fasteners 19, 20 and 21 in place in the assembled position illustrated in Fig. 2, an annular retaining sleeve 23 is seated in outer portion 14 of the vent hole on top of and in engagement with the peripheral portion of outermost fastener 21, and is fixed against outward movement in any suitable manner, as by peening of the metal of the mold wall form ing the outer edge of the vent hole, indicated at 24. As shown in Fig. 2, retaining sleeve 23 has an axial dimension somewhat less than the depth of outer portion 14 of the vent hole, e.g., /3 inch in the case where outer portion 14 is W inch deep, and has an internal diameter such as to provide a substantial clearance between its inner surface and the upper end of core member 17, for a purpose hereinafter described.

In assembling the elements of the vent, the innermost fastener 19 is first pushed onto core member 17 from the end thereof which, in the completed assembly, lies adjacent the inner surface of the mold wall, after which the core member and attached fastener 19 are dropped into the vent hole through outer portion 14 so' that the peripheral portion of the fastener seats against shoulder 16. A back-up jig, indicated in broken lines at 25 in Fig. 2, is' then inserted in the" mold and positioned opposite the inner end of the vent hole, whereupon core member 17 is forced inwardly through fastener 19 until the inner end of the core member comes into abutment with the back-up jig and is thereby made substantially flush with the inner surface of the mold wall. Fasteners 20 and 21 are next pushed onto core member 17 from the outer end thereof until the peripheries of fasteners 20 and 21 abut those of'fasteners 19 and 20, respectively.- Retaining sleeve 23 is then inserted in outer portion 14 of the vent hole and forced downwardly into abutment with the periphery of outermost fastener 21, and the outer edge of the hole is peened over as shown at 24in order to lock the entire assembly in place. While axial movement of the peripheral portions of fasteners 19, 20 and 21 is prevented by shoulder 16 and sleeve 23, the engagement between these elements is not so tight as to prevent rotation of the fasteners within the vent hole.

As will be evident from Figs. 24, venting passageways 18 and the spaces between the flexed teeth 22 of fasteners 19, 2t and 21 provide a ready path of escape for gas from inside the mold. At the same time, however, passageways 18 present such small openings to the interior of the mold that relatively little of the lining material, and none of the molten casting metal, enters the vents. It has been found in practice that vents of this construction permit the free passage of gas for from 60 to castings before they begin to collect obstrucing deposits, such as products of combustion and extremely fine sand, and require cleaning In order to clean the vent shown in Figs. 1-4, it is only necessary to apply a socket wrench or other tool to the outer end of core member 17 in the space between the latter and sleeve 23, and to rotate or oscillate the core member about its axis so that the edges of said member scrape or scour the wall of inner portion 15 of the vent hole, breaking up the deposits and causing them to drop inwardly into the interior of the mold. It will be understood that, as core member 17 is rotated within the vent hole, fasteners 19, 20, and 21 also rotate with the core member between shoulder 16 and sleeve 23.

Although a co're member of hexagonal cross section as shown in Figs. 24 has been found well suited for the purposes of the present invention when used in combination with a vent hole of the dimensions above indicated, it will be obvious that the core member may take various other forms so long as it cooperates with the vent hole to provide a plurality of relatively restricted gas passageways and is so constructed as to be capable of cleaning the vent merely by being rotated about its axis and without requiring removal from the' vent hole of any of the elements of the vent assembly.

As examples of other forms of core members co'ntemplated by the present invention, Figs. 5 and 6 show and views of core members 17 and 17" having cross sections which are square and octagonal, respectively. In the embodiment of Fig. 7, the core member 27 has an outer end 28 of hexagonal cross section, similar to member 17 of Figs. 24, but the main body of the member is of cylindrical form with a plurality of radially outwardly projecting flutes 30, the outer ends of which are adapted to scrape the wall of inner portion 15 of the vent hole when the core member is rotated and thereby perform the same cleaning function as do the edges of members 17, 17 and 17". Fig. 8 illustrates still another modification of the invention comprising a core member 30 having a hexagonal outer end 31 and a cylindrical body provided with a plurality of helical scouring threads or ridges 32 which not only break up whatever deposits may adhere to the wall of the vent hole, but also feed the broken-up material inwardly into the interior of the mold by a sort of auger action. It will be understood that the spaces between flutes 29 in Fig. 7, and those between threads 32 in Fig. 8, form gas venting passageways similar to those shown at 18 in the embodiment of Figs. 2-4. i i

There is thus provided by the present invention a new and improved vent construction for centrifugal casting molds, particularly those wherein linings are formed cen trifugally of materials producing gas during the casting operation, which construction permits the free escape of gas from the interior of the mold while preventing stoppage of the venting passageways by either the lining material or the casting metal, and which is quickly and easily cleaned whenever necessary without removal of any of the elements of the vent assembly.

Although only one complete vent assembly and several modified forms of the core member embodying the invention have been described and illustrated in the accompanying drawing, it will be obvious that the invention is not limited to these particular structures, but is capable of a variety of mechanical embodiments. Various changes, which will now suggest themselves to those skilled in the art, may be made in the shapes, dimensions and other structural details of the elements of the vent, and in the means by which said elements are maintained in properly assembled position, without departing from the inventive concept. Reference is therefore to be had to the appended claims for a definition of the limits of the invention.

What is claimed is:

l. A centrifugal casting mold comprising a hollow substantially cylindrical body having a vent hole extending in a substantially radial direction from the inner surface to the outer surface of the mold body for permitting the escape of gas from the interior of the mold body during the casting operation, and a core member in said vent hole so supported therein as to resist movement axially of said hole while being capable of rotation therewithin, said core member being of less cross-sectional area than said vent hole and cooperating therewith to form a plurality of restricted venting passageways through which gases may escape outwardly from the interior of the mold body, said core member being so shaped that rotation thereof scours the wall of said vent hole.

2. A mold as defined in claim 1 wherein said core member has a plurality of outwardly projecting surfaces adapted to scrape the wall of said vent hole when the core member is rotated.

3. A mold as defined in claim 1 wherein the crosssectional shape of said vent hole and the cross-sectional shape of said core member are circular and polygonal, respectively, and the axial extending edges of said core member are adapted to scrape the wall of said vent hole when the core member is rotated.

4. A mold as defined in claim 3 wherein the crosssectional shape of said core member is hexagonal.

5. A mold as defined in claim 1 wherein said vent hole is circular in cross section and said core member comprises a cylindrical body having a plurality of outwardly projecting flutes thereon adapted to scrape the wall of said vent hole when the core member is rotated.

6. A mold as defined in claim 1 wherein said vent hole is circular in cross section and said core member comprises a cylindrical body having a plurality of outwardly projecting helical ridges thereon adapted to scrape the wall of said vent hole when the core member is rotated.

7. A centrifugal casting mold comprising a hollow substantially cylindrical body having a vent hole extending through the mold body in a substantially radial direction for permitting the escape of gas from the interior of the mold body during the casting operation, a core member coaxial with said vent hole having its inner end substantially flush with the inner surface of the mold body and extending outwardly substantially the entire length of the vent hole, said core member cooperating with the surrounding wall of said vent hole to form a plurality of restricted venting passageways through which gas may escape outwardly from the interior of the mold body, and means for rotatably supporting said core member in an axially fixed position in said vent hole, the cross-sectional 6 shape of said core member being such as to provide a plurality of scraping edges adapted to scour the wall of said vent hole when said member is rotated.

8. A mold as defined in claim 7 wherein the outer end of said core member is so formed as to cooperate with an externally applied tool for rotating said member when it is desired to clean the vent hole.

9. A mold as defined in claim 7 wherein the outer end of said core member is polygonal in cross section and the outer end of said vent hole is of enlarged diameter to enable application of a tool to the outer end of the core member for rotating said member when it is desired to clean the vent hole.

10. A centrifugal casting mold comprising a hollow substantially cylindrical body having a vent hole extending in a substantially radial direction from the inner surface to the outer surface of the mold body for permitting the escape of gas from the interior of the mold body during the casting operation, a core member coaxial with said vent hole and cooperating with the wall thereof to form a plurality of restricted venting passageways through which gas may escape outwardly from the interior of the mold body, the radially outer portion of said vent hole being of greater diameter than the remainder thereof, and means for rotatably supporting said core member in said vent hole, the cross-sectional shape of said core member being such as to provide a plurality of outwardly projecting surfaces adapted to scrape the wall of said vent hole when the core member is rotated, said core supporting means including a push-on fastener having a peripheral portion rotatably housed in the enlarged outer portion of said vent hole and a plurality of inwardly projecting flexible teeth engaging the periphery of said core member and so flexed as to resist movement of said core member outwardly of said vent hole, and means for preventing axial movement of the peripheral portion of said fastener relative to the vent hole.

11. A mold as defined in claim 10 wherein said core member supporting means includes at least one additional push-on fastener having a peripheral portion rotatably housed in the enlarged outer portion of the vent hole and a plurality of inwardly projecting flexible teeth engaging the periphery of said core member and so flexed as to resist movement of said core member inwardly of said vent hole.

12. A mold for use in centrifugally casting tubular metal articles comprising a hollow, substantially cylindrical metal body having a plurality of vent holes therein, each of said vent holes extending in a substantially radial direction from the inner surface to the outer surface of the mold body and having coaxial radially inner and outer portions of different diameters, the inner portion of each vent hole being of less diameter than the outer portion thereof, a core member disposed in each vent hole having an inner portion coextensive in length with the inner portion of said hole and an outer portion positioned in the outer portion of said hole with its outer end adjacent the outer surface of the mold body, the inner portion of said core member cooperating with the surrounding wall of said vent hole to form a plurality of restricted venting passageways through which gas may escape from the interior of the mold body during the casting operation, and means for supporting said core members in said vent holes, said supporting means being so constructed and arranged as to resist movement of said core members axially of said vent holes while permitting rotation of said members within said holes, the inner portion of each of said core members being so formed that rotation thereof scours the wall of the inner portion of the cooperating vent hole, and the outer end of said core member being so formed as to cooperate with an externally applied tool for rotating said member when it is desired to clean the vent hole.

13. A mold as defined in claim 12 wherein the crosssectional shape of the inner portion of each vent hole and the crosssectionalshape'of the inner portion ;of;the cooperating 'core member are circular and polygonal, respectively, and; the axially extendedfedges said; core member are'adaptedtoscrape the surrounding all of the inner portion of said vent hole when the core member is rotated. V e 7 v V j 14. A mold as defined in claim 13 wherein the crosssectional shape of the inner portion of each core member is hexagonal. p p 7 p p 15. A mold as defined in claim 12 wherein both portions of each vent hole are circular in cross section, the inner portion of the cooperating core member comprises a cylindrical body having a plurality of outwardly projecting elements thereon adapted to scrape the wall of the inner portion of said vent hole when the core member is rotated, and the outer end of said core member is polygonal in cross section. 1 H 16. A mold as defined in claim 12 wherein the inner and outer portions of each vent hole are connected by a shoulder, and the cooperating core member supporting means includes a plurality of push-on fastenersrotatably supported on said shoulder and having inwardly projecting flexible teeth engaging the peripheryof the outer portion ofsaidcoremember, I a

17. A mold as defined'in claim 16including a retaining sleeve fixed in the outer portion ofeach vent hole and preventing outward axial movement of said push-on fasteners; the inner surface of said sleeve being spaced from'the outer end of the cooperating core member sufliciently to enable application to the latter of a rotating tool.

References Cited in the file of thisp'atent UNITED STATES PATENTS j 367,774 Adams Aug. 9, 1887 787,325 CoWde-n Apr. 11, 1905 1,552,245 Thompson Sept. 1, 1925 1,570,669 Heinzelman Jan. 26, 1926 2,042,015 Moormann May 26, 1936 

